If you're thinking of the native foxglove (Digitalis purpurea and/or any of it's many colour forms) then this is a biennial, which means that it will almost always die after flowering.

You can sometimes force them to survive into the next year by cutting off the flowering stems before they form seed, but a much better idea is simply to collect and sow some of the vast amount of seed that the plants will produce. In fact they will self-seed themselves anyway, so if you leave them alone you will almost certainly get a good many seedlings coming up around the old plant.

Another thing too......if you cut off the main flowering stem as it begins to fade, you will see more smaller flowering stems to come....this'll prolong its flowering time.

if it is one of the perennial forms then again dead head it and you may get a second flush of blooms. I tend to leave the final flowers on all my foxgloves for them to set seed, this makes sure i will get new plants next year.